The present invention relates to methods and apparatuses for testing structural properties of structural members, more particularly to methods and apparatuses for testing fatigue of structural members having complex joints.
For certain kinds of structural members, conventional approaches to evaluating fatigue have not been entirely satisfactory. In particular, there remains a need for a practical yet accurate fatigue testing methodology for shaft-like structural members containing complex joints at both ends, especially for such members which are made of heterogeneous materials. Generally speaking, systems of complex joints which utilize a variety of materials have unpredictable fatigue characteristics.
The U.S. Navy has conducted cyclic fatigue testing of structural members comprising fiber-reinforced polymer-matrix composite and titanium materials. In order to reduce costs, such testing by the Navy has typically been relegated to small-scale model testing or coupon testing. However, the Navy has had limited success in extrapolating these test results so as to accurately predict full-scale long term fatigue strength for joints which utilize fiber-reinforced polymer-matrix composite and titanium materials in a propulsion shafting system.